Atlanta -LRB- CNN -RRB- -- One of the countries hard hit by the Ebola outbreak in West Africa is not able to cope , a health worker said , calling on the international community to step up support .

Anja Wolz , emergency coordinator for Doctors Without Borders , spoke to CNN on Tuesday from an Ebola facility in Kailahun , Sierra Leone .

`` I think that the government and the ministry of health here in Sierra Leone is not able to deal with this outbreak . We need much more help from international organizations -- as WHO , as CDC , as other organizations -- to come to support the government , '' Wolz said .

`` Still we have unsafe burials ; people who are doing the burial without disinfection of the body ; still we have patients who are hiding themselves ; still we have patients or contacts of patients who are running away because they are afraid . ''

Sierra Leone , Guinea and Liberia are at the center of an Ebola outbreak that has already killed more than 800 people .

The global concern over the spread of the virus has reached Saudi Arabia , where a man is in critical condition after recently returning from Sierra Leone .

The 40-year-old man has symptoms of a viral hemorrhagic fever , the Saudi Health Ministry said Tuesday . The source of his infection is unknown , but Ebola can not be ruled out , the ministry said .

`` This is the biggest and most complex Ebola outbreak in history , '' Dr. Tom Frieden , director of the Centers for Disease Control and Prevention , said in a statement .

`` It will take many months , and it wo n't be easy , but Ebola can be stopped , '' he said . `` We know what needs to be done . ''

The virus has already been confirmed outside of the three main countries .

A Nigerian doctor has been diagnosed with Ebola nearly three weeks after a Liberian-American man with Ebola died after traveling to Lagos , Nigerian officials said Monday .

Nigerian Minister of Health Onyebuchi Chukwu told reporters that the infected physician had been treating Patrick Sawyer , a top government official in the Liberian Ministry of Finance who died of Ebola in a Nigerian hospital July 20 .

Eight other people are being quarantined and three are awaiting Ebola test results , the health minister said .

Read more about Patrick Sawyer 's death

Meanwhile , the World Health Organization reports an outbreak of the virus in Liberia , Sierra Leone , Guinea and Nigeria is believed to have infected 1,603 people and killed more than 887 this year , as of Friday .

The United States is planning to send 50 health experts to West Africa to help contain the outbreak , which President Barack Obama addressed in remarks Tuesday , saying the citizens of the affected countries are in Americans ' thoughts and prayers .

Frieden said the 50 experts from the CDC will work to combat the outbreak and help implement stronger systems to fight the disease .

The Ebola virus causes viral hemorrhagic fever , which affects multiple organ systems in the body and is often accompanied by bleeding .

Early symptoms include sudden onset of fever , weakness , muscle pain , headaches and a sore throat . They later progress to vomiting , diarrhea , impaired kidney and liver function -- and sometimes internal and external bleeding .

An Ebola patient had not been treated within U.S. borders until last week , but the CDC has spearheaded efforts to prepare for the deadly virus .

5 reasons not to panic about Ebola in the U.S. .

It helped create an isolation unit at Emory University Hospital , which is being used to treat American doctor Kent Brantly , who contracted Ebola in Liberia and was evacuated to the facility in Atlanta over the weekend .

A second American patient , Nancy Writebol , arrived from Liberia on Tuesday . She will undergo treatment at the same unit .

Emory is one of four U.S. institutions capable of providing such treatment .

But in the nations hardest-hit and not as prepared , the reality is grim . Even in the best-case scenario , it could take three to six months to stem the epidemic in West Africa , Frieden said .

Ebola spreads through contact with organs and bodily fluids such as blood , saliva , urine and other secretions of infected people . It has no cure . The most common treatment requires supporting organ functions and maintaining bodily fluids such as blood and water long enough for the body to fight off the infection .

Ebola also claimed the life of a medical director at a hospital in Liberia 's capital , Monrovia . Dr. Patrick Nshamdze tested positive Tuesday after being sick for two weeks . He died Saturday .

In Sierra Leone , where government officials have asked citizens to stay away from work , the military has deployed at least 750 medical officials to 13 locations , military spokesman Col. Michael Samura said .

Health officials are screening incoming and outgoing passengers at the country 's main international airport with a device that takes people 's temperature from their eyes at a distance .

People showing signs of fever are quarantined and their blood is tested .

On Tuesday , Liberia responded to British Airways ' decision to suspend service to Monrovia because of the outbreak .

`` The government of Liberia regrets that British Airways has suspended flights to and from Liberia until the end of August . However , we fully understand that international airlines must keep the safety of customers and crew as their highest priority , '' it said .

`` We will continue to work around the clock with our international partners to ensure all our key international ports of entry are secure from any transfer of Ebola , both incoming or outgoing . ''

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CNN 's David McKenzie contributed to this report from Freetown , Sierra Leone . Journalist Heather Murdock reported from Nigeria . CNN 's Fred Pleitgen , Faith Karimi , Nana Karikari-apau and Christabelle Fombu also contributed to this report .

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Sierra Leone , Guinea and Liberia are at the center of an Ebola outbreak

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A man hospitalized in Saudi Arabia has symptoms of a viral hemorrhagic fever

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A Nigerian doctor was diagnosed with Ebola after treating a Ebola patient there

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That diagnosis comes three weeks after a Liberian-American man died from virus